Chest drainage devices are used primarily for removing fluids from the pleural cavity of a patient and generally include a collection chamber a water seal chamber and a suction control chamber. The suction control chamber limits the negative pressure applied to the collection chamber and the pleural cavity of the patient. During operation of a chest drainage device, liquid from the patient's pleural cavity is drawn into and accumulated in the collection chamber. The gas is drawn from the pleural cavity of the patient passed through a water seal in the water seal chamber and into the source of suction. The water seal operates as a barrier to prevent the patient's pleural cavity from being exposed to the atmosphere and also prevents the patient's pleural cavity from being in direct flow communication with the source of suction.
U.S. Pat. No. 3,783,780, issued to Schachet on Jan. 8, 1974, and U.S. Pat. No. 4,439,190, issued to Protzmann et al on March 27, 1984 describe the operation of a typical chest drainage device. Both of the above referenced patents are incorporated herein by reference. The present invention is readily adaptable for use in an integral one piece chest drainage device or a multi bottle chest drainage device similar to the chest drainage devices referenced above.
Generally, the suction control chamber allows the user to apply a prescribed pressure to the pleural cavity of a patient by adding a predetermined amount of liquid to the suction control chamber. The commonly used chest drainage device utilizes a suction control chamber which is basically an unequal legged water manometer to regulate the vacuum pressure being applied to the pleural cavity of a patient. This type of suction control chamber generally consists of a pair of legs or columns interconnected at their bottom ends. The top of the generally smaller, first column, is open to the atmosphere. The second column is generally larger than the first column and includes a top end in flow communication with the vacuum source and the pleural cavity of the patient.
The overall height of the suction control chamber typically dictates the minimum height of the chest drainage device. Commonly available chest drainage devices have an overall height of approximately 40 cm. and in the typical suction control chamber, approximately 25 cm. is attributable to the operational range of the chest drainage device described herein as the suction control section. The remaining height of the chest drainage device is attributable to the air/water separation space located above the suction control section and the height of the base or stand of the chest drainage device.
The effectiveness of the air/water separation space at any given air flow rate is determined by the overall suction control chamber geometry and the height of the suction control chamber above the suction control section. If the air flow rate through the suction control chamber is too high, liquid is entrained in the air and will be carried out of the suction control chamber. If this occurs, the suction pressure being applied to the pleural cavity of the patient will gradually decrease as the liquid level in the suction control chamber is depleted. Additionally, the liquid from the suction control chamber will contaminate the vacuum source and/or be deposited within the other chambers of the chest drainage device. Certain chest drainage devices have incorporated baffles in the top of the suction control chamber in an effort to decrease the required height of the air/water separation space and to prevent the loss of water in the suction control chamber.
In a chest drainage device, the vacuum pressure applied to the pleural cavity of a patient is dependent of the dynamic water height of the liquid in the suction control chamber. For example, if the desired patient pressure is 20 cm. H.sub.2 O of vacuum pressure, a dynamic water height of at least 20 cm. is required in the suction control chamber. In chest drainage devices which utilize a water seal chamber, the water seal chamber will typically add approximately 2 cm. of resistance so that if the desired patient pressure is 20 cm. H.sub.2 O, the suction control chamber must provide 22 cm. H.sub.2 O of vacuum pressure to overcome the increased resistance created by the water seal chamber. The standard operating ranges for most chest drainage devices is between 5 and 25 cm. H.sub.2 O vacuum pressure. Therefore, in order to have the capability of supplying the 25 cm. H.sub.2 O of vacuum pressure to the pleural cavity of the patient, this portion of the suction control chamber must be at least 25 cm. high. The baffle systems used in certain chest drainage devices are designed to reduce the height of the air/water separation space and do not materially effect the dynamic water height of the suction control chamber. Therefore, unless valves or other flow restricting devices are used, the height of a chest drainage device must be at least 25 cm. plus the height of the air/water separation space or baffle chamber in the base of the chest drainage device.